Geodesic structures are popular and well known. Typically, such structures include a network of struts defining the straight-sided geometrical shapes that are joined together to form the overall structure. Geodesic structures having struts forming at least part of a regular icosahedron are particularly popular and are especially successful in constructing relatively small structures.
The struts of geodesic structures typically meet in complicated joints involving several struts meeting at angles that are determined by the particular geometrical shape defined by the entire network of struts. As a consequence, complicated mitering and fitting of the ends of such struts traditionally has been necessary. Such mitering and fitting requires considerable skill on the part of the workmen. Alternatively, factory pre-formed struts may be used in which the mitering and fitting is done in advance.
Various methods and devices have been developed to allow a comparatively unskilled workman to use conventional building materials, such as framing lumber of conventional dimensions, as the struts of geodesic structures. Examples include Birkemeier, et al., U.S. Pat. No. 3,635,509, and Woods, U.S. Pat. No. 3,486,278. A junction plate for use with conventional framing lumber is sold by East-West Design, Inc., Madison, Wis., and is adapted specifically for the construction of a geodesic structure in which the struts define part of a regular icosahedron.
Typically, the conventional framing lumber used as struts in geodesic domes is rectangular in cross section. Usually the struts are so joined that opposite sides of the rectangular framing lumber are held parallel to a line drawn from the center of the geometric shape defined by the network of struts through the center line of the framing member. Thus, the sides of adjacent struts are held at a predetermined angle to each other that reflects the fact that the ends of the struts converge on each other and the opposed sides of two adjacent struts tip away from each other.
It is usually necessary to include in a geodesic structure framing members additional to those constituting the struts that define the geometrical shape of the dome. Such framing members are necessary at any time that a face of the geodesic structure must be subdivided to provide for a window, door, or similar feature. Furthermore, it is sometimes necessary to subdivide the faces of a geodesic dome in order to accommodate sheeting material that is available in pieces too small to cover each face in one unbroken piece. Because of the complicated angles involved, it typically requires a workman of great skill to accomplish the mitering necessary to fit the ends of such a subdividing framing member against the tipped and spreading sides of the struts. Thus, while means have been provided to allow relatively unskilled workmen to construct the basic framework of a geodesic dome without the need to accomplish complicated mitering, great skill still is needed in completing the structure if it is necessary to miter the ends of framing members to subdivide the faces of the structure. This is especially the case because the angles that such framing members make with the struts also may vary from application to application. Thus, while a door frame generally will meet at least one strut at right angles thereto, the framing members defining windows or otherwise subdividing a triangular face of the structure will meet the struts at unpredictable angles.
Various braces and brackets have been developed for attaching one framing member or the like to another in a number of contexts. Examples include Wack, U.S. Pat. No. 4,280,686, Belt, U.S. Pat. No. 4,149,346, Tracy, U.S. Pat. No. 3,596,941, and Tracy, U.S. Pat. No. 3,481,635. However none of the braces or brackets disclosed in the cited patents are adapted to be attached to the strut of a regular icosahedron geodesic structure to receive and hold the unmitered end of a framing member that extends therefrom to another, adjacent strut.